A communication system is formed, at a minimum, of a sending station and a receiving station. The sending and receiving stations are interconnected by way of a communication channel. Information to be communicated by the sending station is sent upon the communication channel by the sending station to the receiving station. A wide variety of different types of communication systems have been developed and implemented to effectuate communication of information between sending and receiving stations.
Advancements in communication technologies have permitted the development of new types of communication systems as well as improvements to existing types of communication systems. A radio system is exemplary of a type of communication system which has benefited from advancements in communication technologies. In a radio communication system, the communication channel which interconnects the sending and receiving stations is formed of a radio link defined of a portion of the electro-magnetic spectrum. Because a radio link is utilized to form the communication channel, a physical connection, conventionally required in a conventional wireline communication system, is obviated.
Because the communication channel is formed upon a radio link in a radio communication system, increased communication mobility is inherently provided in a radio communication system in contrast to that permitted in a conventional wireline communication system. Because a wireline connection is not required to be formed between the sending and receiving stations to permit the communication of information therebetween, communications are permitted at, and between, locations at which formation of a wireline connection would not be possible. Additionally, infrastructure costs associated with a radio communication system are generally less than those associated with a conventional wireline system as radio links are utilized to form communication channels rather than fixed wireline connections.
A cellular communication system is exemplary of a radio communication system which has been made possible due to advancements in communication technologies. A cellular communication system advantageously provides for radio communications with mobile stations to permit telephonic communication therewith. A cellular communication system also makes relatively efficient utilization of the portion of the electromagnetic spectrum allocated thereto and upon which radio channels are defined. The relatively efficient utilization of the allocated electromagnetic spectrum is provided through the installation of a plurality of spaced-apart, fixed-site transceivers installed throughout a geographical area to be encompassed by the cellular communication system. Because of the spaced-apart positioning of the fixed-site transceivers, referred to as base transceiver stations (BTSs), only relatively low-power signals need to be communicated between a base transceiver station and a mobile station. Because of the relatively low-power levels in which the signals are transmitted, the same radio channels can be reused at different locations throughout the cellular communication system as the low power levels of the signal permit reuse of the same channel according to a cell reuse scheme.
Various standards have been promulgated relating to various types of cellular communication systems. The GSM (global system for mobile communications) is exemplary of a standard which sets forth operational parameters for a cellular communication system which utilizes TDMA (time division multiple access) communication techniques. In a GSM system, channels are defined in terms of frequency and a time slot. Each channel is divided into frames, and the frames are further divided into time slots. Therefore, a TDMA communication scheme permits increased communication capacity in contrast with a communication scheme which utilizes conventional analog communication techniques as the bandwidth allocated to communicate thereon is more efficiently utilized.
Power control of communication signals transmitted in almost any communication system is important to reduce the possibility that the communication signal might interfere with another concurrently-generated communication signal. The GSM standard sets forth power control requirements for sending stations operable in a GSM communication system. Conventionally, base transceiver stations operable in a GSM communication system utilize a closed-loop power control scheme in which the power levels at which signals transmitted by a base station are sampled and corrected, as appropriate.
By effectuating power control, the possibility that a too-powerful signal is transmitted to cause co-channel, or other, interference is reduced. And, by effectuating power control, the possibility that a too-weak signal is transmitted to prevent recovery of the informational content of the signal at the receiving station is reduced.
Some GSM systems also provide for packet-based communications. GPRS (general packet radio service), e.g., is implemented in some GSM systems. GPRS messaging utilizes a GMSK (gaussian minimum shift keying) modulation technique. Such a modulation technique is also utilized during the communication of circuit-switched communications.
Incorporation of a higher data rate scheme into GSM systems, referred to as EDGE (enhanced data rates for Global evolution), has been proposed. And EDGE-modulated signal is formed by utilizing 8 PSK (8-phase shift keying) modulation. During the useful part a burst of an EDGE-modulated signal, the signal includes an amplitude modulated component.
When a conventional, GSM power control scheme is utilized to control the power levels at which an EDGE-modulated signal is transmitted, the amplitude modulation interferes with power-control operations. That is to say, a reference signal having the same amplitude modulated component corresponding to the output power levels of the EDGE modulated signal is difficult to match with the detected output signal due to delays and non-linearity associated with formation of the final, output signal at the base transceiver station. As the level of both the reference signal and the output signal subsequent to amplification are unlikely to be identical, the output power levels of output signals generated at the sending station is susceptible to drift due to the inaccuracy of the loop.
A manner by which to better effectuate power control over EDGE-modulated signals, or other amplitude-modulated signals would facilitate improved power control and, correspondingly, permit improved communication system performance.
It is in light of this background information related to the effectuation of power control in a communication system that the significant improvements of the present invention have evolved.